summaryrefslogtreecommitdiff
path: root/src/backenddb/plugin_merchantdb_postgres.c
blob: 76d4efee291e131bb2f1dd67d5d5992e1c64ba8b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
/*
  This file is part of TALER
  (C) 2014, 2015, 2016, 2017 INRIA

  TALER is free software; you can redistribute it and/or modify it under the
  terms of the GNU Lesser General Public License as published by the Free Software
  Foundation; either version 3, or (at your option) any later version.

  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

  You should have received a copy of the GNU General Public License along with
  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
*/
/**
 * @file merchant/plugin_merchantdb_postgres.c
 * @brief database helper functions for postgres used by the merchant
 * @author Sree Harsha Totakura <sreeharsha@totakura.in>
 * @author Christian Grothoff
 * @author Marcello Stanisci
 */
#include "platform.h"
#include <gnunet/gnunet_util_lib.h>
#include <gnunet/gnunet_pq_lib.h>
#include <taler/taler_util.h>
#include <taler/taler_pq_lib.h>
#include <taler/taler_json_lib.h>
#include "taler_merchantdb_plugin.h"


/**
 * Type of the "cls" argument given to each of the functions in
 * our API.
 */
struct PostgresClosure
{

  /**
   * Postgres connection handle.
   */
  PGconn *conn;

  /**
   * Underlying configuration.
   */
  const struct GNUNET_CONFIGURATION_Handle *cfg;

};


/**
 * Drop merchant tables
 *
 * @param cls closure our `struct Plugin`
 * @return #GNUNET_OK upon success; #GNUNET_SYSERR upon failure
 */
static int
postgres_drop_tables (void *cls)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_ExecuteStatement es[] = {
    GNUNET_PQ_make_try_execute ("DROP TABLE merchant_transfers;"),
    GNUNET_PQ_make_try_execute ("DROP TABLE merchant_deposits;"),
    GNUNET_PQ_make_try_execute ("DROP TABLE merchant_transactions;"),
    GNUNET_PQ_make_try_execute ("DROP TABLE merchant_proofs;"),
    GNUNET_PQ_make_try_execute ("DROP TABLE merchant_contract_terms;"),
    GNUNET_PQ_make_try_execute ("DROP TABLE merchant_refunds;"),
    GNUNET_PQ_EXECUTE_STATEMENT_END
  };

  return GNUNET_PQ_exec_statements (pg->conn,
                                    es);
}


/**
 * Initialize merchant tables
 *
 * @param cls closure our `struct Plugin`
 * @return #GNUNET_OK upon success; #GNUNET_SYSERR upon failure
 */
static int
postgres_initialize (void *cls)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_ExecuteStatement es[] = {
    GNUNET_PQ_make_execute ("CREATE TABLE IF NOT EXISTS merchant_contract_terms ("
                            "order_id VARCHAR NOT NULL"
                            ",merchant_pub BYTEA NOT NULL"
                            ",contract_terms BYTEA NOT NULL"
                            ",h_contract_terms BYTEA NOT NULL"
                            ",timestamp INT8 NOT NULL"
                            ",row_id BIGSERIAL UNIQUE"
                            ",paid BYTEA NOT NULL "
                            ",PRIMARY KEY (order_id, merchant_pub)"
			    ",UNIQUE (h_contract_terms, merchant_pub)"
                            ");"),
    GNUNET_PQ_make_execute ("CREATE TABLE IF NOT EXISTS merchant_refunds ("
                            " rtransaction_id BIGSERIAL UNIQUE"
                            ",merchant_pub BYTEA NOT NULL CHECK (LENGTH(merchant_pub)=32)"
                            ",h_contract_terms BYTEA NOT NULL"
                            ",coin_pub BYTEA NOT NULL CHECK (LENGTH(coin_pub)=32)"
                            ",reason VARCHAR NOT NULL"
                            ",refund_amount_val INT8 NOT NULL"
                            ",refund_amount_frac INT4 NOT NULL"
                            ",refund_amount_curr VARCHAR(" TALER_CURRENCY_LEN_STR ") NOT NULL"
                            ",refund_fee_val INT8 NOT NULL"
                            ",refund_fee_frac INT4 NOT NULL"
                            ",refund_fee_curr VARCHAR(" TALER_CURRENCY_LEN_STR ") NOT NULL"
                            ");"),
    GNUNET_PQ_make_execute ("CREATE TABLE IF NOT EXISTS merchant_transactions ("
                            " h_contract_terms BYTEA NOT NULL"
                            ",exchange_uri VARCHAR NOT NULL"
                            ",merchant_pub BYTEA NOT NULL CHECK (LENGTH(merchant_pub)=32)"
                            ",h_wire BYTEA NOT NULL CHECK (LENGTH(h_wire)=64)"
                            ",timestamp INT8 NOT NULL"
                            ",refund_deadline INT8 NOT NULL"
                            ",total_amount_val INT8 NOT NULL"
                            ",total_amount_frac INT4 NOT NULL"
                            ",total_amount_curr VARCHAR(" TALER_CURRENCY_LEN_STR ") NOT NULL"
                            ",PRIMARY KEY (h_contract_terms, merchant_pub)"
                            ");"),
    GNUNET_PQ_make_execute ("CREATE TABLE IF NOT EXISTS merchant_deposits ("
                            " h_contract_terms BYTEA NOT NULL"
                            ",merchant_pub BYTEA NOT NULL CHECK (LENGTH(merchant_pub)=32)"
                            ",FOREIGN KEY (h_contract_terms, merchant_pub) REFERENCES merchant_transactions (h_contract_terms, merchant_pub)"
                            ",coin_pub BYTEA NOT NULL CHECK (LENGTH(coin_pub)=32)"
                            ",amount_with_fee_val INT8 NOT NULL"
                            ",amount_with_fee_frac INT4 NOT NULL"
                            ",amount_with_fee_curr VARCHAR(" TALER_CURRENCY_LEN_STR ") NOT NULL"
                            ",deposit_fee_val INT8 NOT NULL"
                            ",deposit_fee_frac INT4 NOT NULL"
                            ",deposit_fee_curr VARCHAR(" TALER_CURRENCY_LEN_STR ") NOT NULL"
                            ",refund_fee_val INT8 NOT NULL"
                            ",refund_fee_frac INT4 NOT NULL"
                            ",refund_fee_curr VARCHAR(" TALER_CURRENCY_LEN_STR ") NOT NULL"
                            ",signkey_pub BYTEA NOT NULL CHECK (LENGTH(signkey_pub)=32)"
                            ",exchange_proof BYTEA NOT NULL"
                            ",PRIMARY KEY (h_contract_terms, coin_pub)"
                            ");"),
    GNUNET_PQ_make_execute ("CREATE TABLE IF NOT EXISTS merchant_proofs ("
                            " exchange_uri VARCHAR NOT NULL"
                            ",wtid BYTEA CHECK (LENGTH(wtid)=32)"
                            ",execution_time INT8 NOT NULL"
                            ",signkey_pub BYTEA NOT NULL CHECK (LENGTH(signkey_pub)=32)"
                            ",proof BYTEA NOT NULL"
                            ",PRIMARY KEY (wtid, exchange_uri)"
                            ");"),
    /* Note that h_contract_terms + coin_pub may actually be unknown to
       us, e.g. someone else deposits something for us at the exchange.
       Hence those cannot be foreign keys into deposits/transactions! */
    GNUNET_PQ_make_execute ("CREATE TABLE IF NOT EXISTS merchant_transfers ("
                            " h_contract_terms BYTEA NOT NULL"
                            ",coin_pub BYTEA NOT NULL CHECK (LENGTH(coin_pub)=32)"
                            ",wtid BYTEA NOT NULL CHECK (LENGTH(wtid)=32)"
                            ",PRIMARY KEY (h_contract_terms, coin_pub)"
                            ");"),
    GNUNET_PQ_make_try_execute ("CREATE INDEX IF NOT EXISTS merchant_transfers_by_coin"
                                " ON merchant_transfers (h_contract_terms, coin_pub)"),
    GNUNET_PQ_make_try_execute ("CREATE INDEX IF NOT EXISTS merchant_transfers_by_wtid"
                                " ON merchant_transfers (wtid)"),
    GNUNET_PQ_make_execute ("CREATE TABLE IF NOT EXISTS exchange_wire_fees ("
			    " exchange_pub BYTEA NOT NULL CHECK (length(exchange_pub)=32)"
			    ",h_wire_method BYTEA NOT NULL CHECK (length(h_wire_method)=64)"
                            ",wire_fee_val INT8 NOT NULL"
                            ",wire_fee_frac INT4 NOT NULL"
                            ",wire_fee_curr VARCHAR(" TALER_CURRENCY_LEN_STR ") NOT NULL"
                            ",closing_fee_val INT8 NOT NULL"
                            ",closing_fee_frac INT4 NOT NULL"
                            ",closing_fee_curr VARCHAR(" TALER_CURRENCY_LEN_STR ") NOT NULL"
			    ",start_date INT8 NOT NULL"
			    ",end_date INT8 NOT NULL"
			    ",exchange_sig BYTEA NOT NULL CHECK (length(exchange_sig)=64)"
			    ",PRIMARY KEY (exchange_pub,h_wire_method,start_date,end_date)"
			    ");"),
    GNUNET_PQ_EXECUTE_STATEMENT_END
  };
  struct GNUNET_PQ_PreparedStatement ps[] = {
    GNUNET_PQ_make_prepare ("insert_transaction",
                            "INSERT INTO merchant_transactions"
                            "(h_contract_terms"
                            ",exchange_uri"
                            ",merchant_pub"
                            ",h_wire"
                            ",timestamp"
                            ",refund_deadline"
                            ",total_amount_val"
                            ",total_amount_frac"
                            ",total_amount_curr"
                            ") VALUES "
                            "($1, $2, $3, $4, $5, $6, $7, $8, $9)",
                            9),
    GNUNET_PQ_make_prepare ("insert_deposit",
                            "INSERT INTO merchant_deposits"
                            "(h_contract_terms"
                            ",merchant_pub"
                            ",coin_pub"
                            ",amount_with_fee_val"
                            ",amount_with_fee_frac"
                            ",amount_with_fee_curr"
                            ",deposit_fee_val"
                            ",deposit_fee_frac"
                            ",deposit_fee_curr"
                            ",refund_fee_val"
                            ",refund_fee_frac"
                            ",refund_fee_curr"
                            ",signkey_pub"
                            ",exchange_proof) VALUES "
                            "($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14)",
                            14),
    GNUNET_PQ_make_prepare ("insert_transfer",
                            "INSERT INTO merchant_transfers"
                            "(h_contract_terms"
                            ",coin_pub"
                            ",wtid) VALUES "
                            "($1, $2, $3)",
                            3),
    GNUNET_PQ_make_prepare ("insert_refund",
                            "INSERT INTO merchant_refunds"
                            "(merchant_pub"
                            ",h_contract_terms"
                            ",coin_pub"
                            ",reason"
                            ",refund_amount_val"
                            ",refund_amount_frac"
                            ",refund_amount_curr"
                            ",refund_fee_val"
                            ",refund_fee_frac"
                            ",refund_fee_curr"
                            ") VALUES"
                            "($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)",
                            10),
    GNUNET_PQ_make_prepare ("insert_proof",
                            "INSERT INTO merchant_proofs"
                            "(exchange_uri"
                            ",wtid"
                            ",execution_time"
                            ",signkey_pub"
                            ",proof) VALUES "
                            "($1, $2, $3, $4, $5)",
                            5),
    GNUNET_PQ_make_prepare ("insert_contract_terms",
                            "INSERT INTO merchant_contract_terms"
                            "(order_id"
                            ",merchant_pub"
                            ",timestamp"
                            ",paid"
                            ",contract_terms"
                            ",h_contract_terms)"
                            " VALUES "
                            "($1, $2, $3, $4, $5, $6)",
                            6),
    GNUNET_PQ_make_prepare ("mark_proposal_paid",
                            "UPDATE merchant_contract_terms SET"
                            " paid=$1 WHERE h_contract_terms=$2"
                            " AND merchant_pub=$3",
                            3),
    GNUNET_PQ_make_prepare ("insert_wire_fee",
                            "INSERT INTO exchange_wire_fees"
                            "(exchange_pub"
                            ",h_wire_method"
                            ",wire_fee_val"
                            ",wire_fee_frac"
                            ",wire_fee_curr"
                            ",closing_fee_val"
                            ",closing_fee_frac"
                            ",closing_fee_curr"
                            ",start_date"
                            ",end_date"
                            ",exchange_sig)"
                            " VALUES "
                            "($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11)",
                            11),
    GNUNET_PQ_make_prepare ("lookup_wire_fee",
                            "SELECT"
                            " wire_fee_val"
                            ",wire_fee_frac"
                            ",wire_fee_curr"
                            ",closing_fee_val"
                            ",closing_fee_frac"
                            ",closing_fee_curr"
                            ",start_date"
                            ",end_date"
                            ",exchange_sig"
                            " FROM exchange_wire_fees"
                            " WHERE exchange_pub=$1"
			    "   AND h_wire_method=$2"
			    "   AND start_date <= $3"
			    "   AND end_date > $3",
                            1),
    GNUNET_PQ_make_prepare ("find_contract_terms_from_hash",
                            "SELECT"
                            " contract_terms"
                            " FROM merchant_contract_terms"
                            " WHERE h_contract_terms=$1"
                            "   AND merchant_pub=$2",
                            2),
    GNUNET_PQ_make_prepare ("end_transaction",
                            "COMMIT",
                            0),

    /*NOTE: minimal version, to be expanded on a needed basis*/
    GNUNET_PQ_make_prepare ("find_refunds",
                            "SELECT"
                            " refund_amount_val"
                            ",refund_amount_frac"
                            ",refund_amount_curr"
                            " FROM merchant_refunds"
                            " WHERE coin_pub=$1",
                            1),
    GNUNET_PQ_make_prepare ("find_contract_terms_history",
                            "SELECT"
                            " contract_terms"
                            " FROM merchant_contract_terms"
                            " WHERE"
                            " order_id=$1"
                            " AND merchant_pub=$2"
                            " AND paid=$3",
                            3),
    GNUNET_PQ_make_prepare ("find_contract_terms",
                            "SELECT"
                            " contract_terms"
                            " FROM merchant_contract_terms"
                            " WHERE"
                            " order_id=$1"
                            " AND merchant_pub=$2",
                            2),

    GNUNET_PQ_make_prepare ("find_contract_terms_by_date",
                            "SELECT"
                            " contract_terms"
                            ",order_id"
                            ",row_id"
                            " FROM merchant_contract_terms"
                            " WHERE"
                            " timestamp<$1"
                            " AND merchant_pub=$2"
                            " AND paid=$4"
                            " ORDER BY row_id DESC, timestamp DESC"
                            " LIMIT $3",
                            4),
    GNUNET_PQ_make_prepare ("find_refunds_from_contract_terms_hash",
                            "SELECT"
			    " coin_pub"
			    ",rtransaction_id"
			    ",refund_amount_val"
			    ",refund_amount_frac"
			    ",refund_amount_curr"
			    ",refund_fee_val"
			    ",refund_fee_frac"
			    ",refund_fee_curr"
			    ",reason"
			    " FROM merchant_refunds"
                            " WHERE merchant_pub=$1"
                            " AND h_contract_terms=$2",
                            2),
    GNUNET_PQ_make_prepare ("find_contract_terms_by_date_and_range",
                            "SELECT"
                            " contract_terms"
                            ",order_id"
                            ",row_id"
                            " FROM merchant_contract_terms"
                            " WHERE"
                            " timestamp<$1"
                            " AND merchant_pub=$2"
                            " AND row_id<$3"
                            " AND paid=$5"
                            " ORDER BY row_id DESC, timestamp DESC"
                            " LIMIT $4",
                            5),
    GNUNET_PQ_make_prepare ("find_contract_terms_by_date_and_range_future",
                            "SELECT"
                            " contract_terms"
                            ",order_id"
                            ",row_id"
                            " FROM merchant_contract_terms"
                            " WHERE"
                            " timestamp>$1"
                            " AND merchant_pub=$2"
                            " AND row_id>$3"
                            " AND paid=$5"
                            " ORDER BY row_id DESC, timestamp DESC"
                            " LIMIT $4",
                            5),
    GNUNET_PQ_make_prepare ("find_transaction",
                            "SELECT"
                            " exchange_uri"
                            ",h_wire"
                            ",timestamp"
                            ",refund_deadline"
                            ",total_amount_val"
                            ",total_amount_frac"
                            ",total_amount_curr"
                            " FROM merchant_transactions"
                            " WHERE h_contract_terms=$1"
                            " AND merchant_pub=$2",
                            2),
    GNUNET_PQ_make_prepare ("find_deposits",
                            "SELECT"
                            " coin_pub"
                            ",amount_with_fee_val"
                            ",amount_with_fee_frac"
                            ",amount_with_fee_curr"
                            ",deposit_fee_val"
                            ",deposit_fee_frac"
                            ",deposit_fee_curr"
                            ",refund_fee_val"
                            ",refund_fee_frac"
                            ",refund_fee_curr"
                            ",exchange_proof"
                            " FROM merchant_deposits"
                            " WHERE h_contract_terms=$1"
                            " AND merchant_pub=$2",
                            2),
    GNUNET_PQ_make_prepare ("find_deposits_by_hash_and_coin",
                            "SELECT"
                            " amount_with_fee_val"
                            ",amount_with_fee_frac"
                            ",amount_with_fee_curr"
                            ",deposit_fee_val"
                            ",deposit_fee_frac"
                            ",deposit_fee_curr"
                            ",refund_fee_val"
                            ",refund_fee_frac"
                            ",refund_fee_curr"
                            ",exchange_proof"
                            " FROM merchant_deposits"
                            " WHERE h_contract_terms=$1"
                            " AND merchant_pub=$2"
                            " AND coin_pub=$3",
                            3),
    GNUNET_PQ_make_prepare ("find_transfers_by_hash",
                            "SELECT"
                            " coin_pub"
                            ",wtid"
                            ",merchant_proofs.execution_time"
                            ",merchant_proofs.proof"
                            " FROM merchant_transfers"
                            "   JOIN merchant_proofs USING (wtid)"
                            " WHERE h_contract_terms=$1",
                            1),
    GNUNET_PQ_make_prepare ("find_deposits_by_wtid",
                            "SELECT"
                            " merchant_transfers.h_contract_terms"
                            ",merchant_transfers.coin_pub"
                            ",merchant_deposits.amount_with_fee_val"
                            ",merchant_deposits.amount_with_fee_frac"
                            ",merchant_deposits.amount_with_fee_curr"
                            ",merchant_deposits.deposit_fee_val"
                            ",merchant_deposits.deposit_fee_frac"
                            ",merchant_deposits.deposit_fee_curr"
                            ",merchant_deposits.refund_fee_val"
                            ",merchant_deposits.refund_fee_frac"
                            ",merchant_deposits.refund_fee_curr"
                            ",merchant_deposits.exchange_proof"
                            " FROM merchant_transfers"
                            "   JOIN merchant_deposits"
                            "     ON (merchant_deposits.h_contract_terms = merchant_transfers.h_contract_terms"
                            "       AND"
                            "         merchant_deposits.coin_pub = merchant_transfers.coin_pub)"
                            " WHERE wtid=$1",
                            1),
    GNUNET_PQ_make_prepare ("find_proof_by_wtid",
                            "SELECT"
                            " proof"
                            " FROM merchant_proofs"
                            " WHERE wtid=$1"
                            "  AND exchange_uri=$2",
                            2),
    GNUNET_PQ_PREPARED_STATEMENT_END
  };

  if (GNUNET_OK !=
      GNUNET_PQ_exec_statements (pg->conn,
                                 es))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }

  if (GNUNET_OK !=
      GNUNET_PQ_prepare_statements (pg->conn,
                                    ps))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Check that the database connection is still up.
 *
 * @param pg connection to check
 */
static void
check_connection (struct PostgresClosure *pg)
{
  if (CONNECTION_BAD != PQstatus (pg->conn))
    return;
  PQfinish (pg->conn);
  pg->conn = GNUNET_PQ_connect_with_cfg (pg->cfg,
                                         "merchantdb-postgres");
  GNUNET_break (NULL != pg->conn);
  GNUNET_break (GNUNET_OK ==
		postgres_initialize (pg));
}


/**
 * Start a transaction.
 *
 * @param cls the `struct PostgresClosure` with the plugin-specific state
 * @return #GNUNET_OK on success
 */
int
postgres_start (void *cls)
{
  struct PostgresClosure *pg = cls;
  PGresult *result;
  ExecStatusType ex;

  check_connection (pg);
  result = PQexec (pg->conn,
                   "START TRANSACTION ISOLATION LEVEL SERIALIZABLE");
  if (PGRES_COMMAND_OK !=
      (ex = PQresultStatus (result)))
  {
    TALER_LOG_ERROR ("Failed to start transaction (%s): %s\n",
                     PQresStatus (ex),
                     PQerrorMessage (pg->conn));
    GNUNET_break (0);
    PQclear (result);
    return GNUNET_SYSERR;
  }
  PQclear (result);
  return GNUNET_OK;
}


/**
 * Roll back the current transaction of a database connection.
 *
 * @param cls the `struct PostgresClosure` with the plugin-specific state
 * @return #GNUNET_OK on success
 */
void
postgres_rollback (void *cls)
{
  struct PostgresClosure *pg = cls;
  PGresult *result;

  result = PQexec (pg->conn,
                   "ROLLBACK");
  GNUNET_break (PGRES_COMMAND_OK ==
                PQresultStatus (result));
  PQclear (result);
}


/**
 * Commit the current transaction of a database connection.
 *
 * @param cls the `struct PostgresClosure` with the plugin-specific state
 * @return transaction status code
 */
static enum GNUNET_DB_QueryStatus
postgres_commit (void *cls)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_end
  };

  return GNUNET_PQ_eval_prepared_non_select (pg->conn,
					     "end_transaction",
					     params);
}


/**
 * Retrieve proposal data given its proposal data's hashcode
 *
 * @param cls closure
 * @param contract_terms where to store the retrieved proposal data
 * @param h_contract_terms proposal data's hashcode that will be used to
 * perform the lookup
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_find_contract_terms_from_hash (void *cls,
                                       json_t **contract_terms,
                                       const struct GNUNET_HashCode *h_contract_terms,
                                       const struct TALER_MerchantPublicKeyP *merchant_pub)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (h_contract_terms),
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_end
  };
  struct GNUNET_PQ_ResultSpec rs[] = {
    TALER_PQ_result_spec_json ("contract_terms",
                               contract_terms),
    GNUNET_PQ_result_spec_end
  };

  check_connection (pg);
  return GNUNET_PQ_eval_prepared_singleton_select (pg->conn,
						   "find_contract_terms_from_hash",
						   params,
						   rs);
}


/**
 * Retrieve proposal data given its order id.  Ignores if the
 * proposal has been paid or not.
 *
 * @param cls closure
 * @param[out] contract_terms where to store the retrieved contract terms
 * @param order id order id used to perform the lookup
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_find_contract_terms (void *cls,
                              json_t **contract_terms,
                              const char *order_id,
                              const struct TALER_MerchantPublicKeyP *merchant_pub)
{
  struct PostgresClosure *pg = cls;

  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_string (order_id),
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_end
  };
  struct GNUNET_PQ_ResultSpec rs[] = {
    TALER_PQ_result_spec_json ("contract_terms",
                               contract_terms),
    GNUNET_PQ_result_spec_end
  };

  *contract_terms = NULL;
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Finding contract term, order_id: '%s', merchant_pub: '%s'.\n",
              order_id,
              TALER_B2S (merchant_pub));
  check_connection (pg);
  return GNUNET_PQ_eval_prepared_singleton_select (pg->conn,
						   "find_contract_terms",
						   params,
						   rs);
}


/**
 * Insert proposal data and its hashcode into db
 *
 * @param cls closure
 * @param order_id identificator of the proposal being stored
 * @param contract_terms proposal data to store
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_insert_contract_terms (void *cls,
                               const char *order_id,
                               const struct TALER_MerchantPublicKeyP *merchant_pub,
                               struct GNUNET_TIME_Absolute timestamp,
                               const json_t *contract_terms)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_HashCode h_contract_terms;
  unsigned int no = GNUNET_NO;

  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_string (order_id),
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_absolute_time (&timestamp),
    GNUNET_PQ_query_param_auto_from_type (&no),
    TALER_PQ_query_param_json (contract_terms),
    GNUNET_PQ_query_param_auto_from_type (&h_contract_terms),
    GNUNET_PQ_query_param_end
  };

  if (GNUNET_OK !=
      TALER_JSON_hash (contract_terms,
		       &h_contract_terms))
    return GNUNET_SYSERR;
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "inserting contract_terms: order_id: %s, merchant_pub: %s, h_contract_terms: %s.\n",
              order_id,
              TALER_B2S (merchant_pub),
              GNUNET_h2s (&h_contract_terms));
  check_connection (pg);
  return GNUNET_PQ_eval_prepared_non_select (pg->conn,
					     "insert_contract_terms",
					     params);
}

/**
 * Mark contract terms as payed.  Needed by /history as only payed
 * contracts must be shown.  NOTE: we can't get the list of (payed)
 * contracts from the transactions table because it lacks contract_terms
 * plain JSON.  In facts, the protocol doesn't allow to store contract_terms
 * in transactions table, as /pay handler doesn't receive this data
 * (only /proposal does).
 */
enum GNUNET_DB_QueryStatus
postgres_mark_proposal_paid (void *cls,
                             const struct GNUNET_HashCode *h_contract_terms,
                             const struct TALER_MerchantPublicKeyP *merchant_pub)
{
  unsigned int yes = GNUNET_YES;
  struct PostgresClosure *pg = cls;

  TALER_LOG_DEBUG ("Marking proposal paid, h_contract_terms: '%s',"
                   " merchant_pub: '%s'\n",
                   GNUNET_h2s (h_contract_terms),
                   TALER_B2S (merchant_pub));

  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (&yes),
    GNUNET_PQ_query_param_auto_from_type (h_contract_terms),
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_end
  };

  return GNUNET_PQ_eval_prepared_non_select (pg->conn,
                                             "mark_proposal_paid",
                                             params);
}


/**
 * Insert transaction data into the database.
 *
 * @param cls closure
 * @param h_contract_terms hashcode of the proposal data associated with the
 * transaction being stored
 * @param merchant_pub merchant's public key
 * @param exchange_uri URI of the exchange
 * @param h_wire hash of our wire details
 * @param timestamp time of the confirmation
 * @param refund refund deadline
 * @param total_amount total amount we receive for the contract after fees
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_store_transaction (void *cls,
                            const struct GNUNET_HashCode *h_contract_terms,
			    const struct TALER_MerchantPublicKeyP *merchant_pub,
                            const char *exchange_uri,
                            const struct GNUNET_HashCode *h_wire,
                            struct GNUNET_TIME_Absolute timestamp,
                            struct GNUNET_TIME_Absolute refund,
                            const struct TALER_Amount *total_amount)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (h_contract_terms),
    GNUNET_PQ_query_param_string (exchange_uri),
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_auto_from_type (h_wire),
    GNUNET_PQ_query_param_absolute_time (&timestamp),
    GNUNET_PQ_query_param_absolute_time (&refund),
    TALER_PQ_query_param_amount (total_amount),
    GNUNET_PQ_query_param_end
  };

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Storing transaction with h_contract_terms '%s', merchant_pub '%s'.\n",
              GNUNET_h2s (h_contract_terms),
              TALER_B2S (merchant_pub));
  check_connection (pg);
  return GNUNET_PQ_eval_prepared_non_select (pg->conn,
					     "insert_transaction",
					     params);
}


/**
 * Insert payment confirmation from the exchange into the database.
 *
 * @param cls closure
 * @param order_id identificator of the proposal associated with this revenue
 * @param merchant_pub merchant's public key
 * @param coin_pub public key of the coin
 * @param amount_with_fee amount the exchange will deposit for this coin
 * @param deposit_fee fee the exchange will charge for this coin
 * @param refund_fee fee the exchange will charge for refunding this coin
 * @param signkey_pub public key used by the exchange for @a exchange_proof
 * @param exchange_proof proof from exchange that coin was accepted
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_store_deposit (void *cls,
                        const struct GNUNET_HashCode *h_contract_terms,
                        const struct TALER_MerchantPublicKeyP *merchant_pub,
                        const struct TALER_CoinSpendPublicKeyP *coin_pub,
                        const struct TALER_Amount *amount_with_fee,
                        const struct TALER_Amount *deposit_fee,
                        const struct TALER_Amount *refund_fee,
                        const struct TALER_ExchangePublicKeyP *signkey_pub,
                        const json_t *exchange_proof)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (h_contract_terms),
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_auto_from_type (coin_pub),
    TALER_PQ_query_param_amount (amount_with_fee),
    TALER_PQ_query_param_amount (deposit_fee),
    TALER_PQ_query_param_amount (refund_fee),
    GNUNET_PQ_query_param_auto_from_type (signkey_pub),
    TALER_PQ_query_param_json (exchange_proof),
    GNUNET_PQ_query_param_end
  };

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "storing payment for h_contract_terms '%s'"
              ", coin_pub: %s, amount_with_fee: %s, merchant_pub: %s\n",
              GNUNET_h2s (h_contract_terms),
              TALER_B2S (coin_pub),
              TALER_amount_to_string (amount_with_fee),
              TALER_B2S (merchant_pub));
  check_connection (pg);
  return GNUNET_PQ_eval_prepared_non_select (pg->conn,
					     "insert_deposit",
					     params);
}


/**
 * Insert mapping of @a coin_pub and @a h_contract_terms to
 * corresponding @a wtid.
 *
 * @param cls closure
 * @param h_contract_terms hashcode of the proposal data paid by @a coin_pub
 * @param coin_pub public key of the coin
 * @param wtid identifier of the wire transfer in which the exchange
 *             send us the money for the coin deposit
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_store_coin_to_transfer (void *cls,
                                 const struct GNUNET_HashCode *h_contract_terms,
                                 const struct TALER_CoinSpendPublicKeyP *coin_pub,
                                 const struct TALER_WireTransferIdentifierRawP *wtid)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (h_contract_terms),
    GNUNET_PQ_query_param_auto_from_type (coin_pub),
    GNUNET_PQ_query_param_auto_from_type (wtid),
    GNUNET_PQ_query_param_end
  };

  check_connection (pg);
  return GNUNET_PQ_eval_prepared_non_select (pg->conn,
					     "insert_transfer",
					     params);
}


/**
 * Insert wire transfer confirmation from the exchange into the database.
 *
 * @param cls closure
 * @param exchange_uri URI of the exchange
 * @param wtid identifier of the wire transfer
 * @param execution_time when was @a wtid executed
 * @param signkey_pub public key used by the exchange for @a exchange_proof
 * @param exchange_proof proof from exchange about what the deposit was for
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_store_transfer_to_proof (void *cls,
                                  const char *exchange_uri,
                                  const struct TALER_WireTransferIdentifierRawP *wtid,
                                  struct GNUNET_TIME_Absolute execution_time,
                                  const struct TALER_ExchangePublicKeyP *signkey_pub,
                                  const json_t *exchange_proof)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_string (exchange_uri),
    GNUNET_PQ_query_param_auto_from_type (wtid),
    GNUNET_PQ_query_param_absolute_time (&execution_time),
    GNUNET_PQ_query_param_auto_from_type (signkey_pub),
    TALER_PQ_query_param_json (exchange_proof),
    GNUNET_PQ_query_param_end
  };

  check_connection (pg);
  return GNUNET_PQ_eval_prepared_non_select (pg->conn,
					     "insert_proof",
					     params);
}


/**
 * Lookup for a proposal, respecting the signature used by the
 * /history's db methods.
 *
 * @param cls db plugin handle
 * @param order_id order id used to search for the proposal data
 * @param merchant_pub public key of the merchant using this method
 * @param cb the callback
 * @param cb_cls closure to pass to the callback
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_find_contract_terms_history (void *cls,
				      const char *order_id,
				      const struct TALER_MerchantPublicKeyP *merchant_pub,
				      TALER_MERCHANTDB_ProposalDataCallback cb,
				      void *cb_cls)
{
  struct PostgresClosure *pg = cls;
  json_t *contract_terms;
  enum GNUNET_DB_QueryStatus qs;
  unsigned int yes = GNUNET_YES;

  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_string (order_id),
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_auto_from_type (&yes),
    GNUNET_PQ_query_param_end
  };
  struct GNUNET_PQ_ResultSpec rs[] = {
    TALER_PQ_result_spec_json ("contract_terms",
                               &contract_terms),
    GNUNET_PQ_result_spec_end
  };

  qs = GNUNET_PQ_eval_prepared_singleton_select (pg->conn,
						 "find_contract_terms_history",
						 params,
						 rs);
  if (qs <= 0)
    return qs;
  cb (cb_cls,
      order_id,
      0,
      contract_terms);
  GNUNET_PQ_cleanup_result (rs);
  return qs;
}


/**
 * Closure for #find_contracts_cb().
 */
struct FindContractsContext
{
  /**
   * Function to call on each result.
   */
  TALER_MERCHANTDB_ProposalDataCallback cb;

  /**
   * Closure for @e cb.
   */
  void *cb_cls;

  /**
   * Transaction status code to set.
   */
  enum GNUNET_DB_QueryStatus qs;
};


/**
 * Function to be called with the results of a SELECT statement
 * that has returned @a num_results results.
 *
 * @param cls of type `struct FindContractsContext *`
 * @param result the postgres result
 * @param num_result the number of results in @a result
 */
static void
find_contracts_cb (void *cls,
		   PGresult *result,
		   unsigned int num_results)
{
  struct FindContractsContext *fcctx = cls;

  for (unsigned int i = 0; i < num_results; i++)
  {
    char *order_id;
    json_t *contract_terms;
    uint64_t row_id;
    struct GNUNET_PQ_ResultSpec rs[] = {
      GNUNET_PQ_result_spec_string ("order_id",
                                    &order_id),
      TALER_PQ_result_spec_json ("contract_terms",
                                 &contract_terms),
      GNUNET_PQ_result_spec_uint64 ("row_id",
                                    &row_id),
      GNUNET_PQ_result_spec_end
    };

    if (GNUNET_OK !=
        GNUNET_PQ_extract_result (result,
                                  rs,
                                  i))
    {
      GNUNET_break (0);
      fcctx->qs = GNUNET_DB_STATUS_HARD_ERROR;
      return;
    }
    fcctx->qs = i + 1;
    fcctx->cb (fcctx->cb_cls,
	       order_id,
	       row_id,
	       contract_terms);
    GNUNET_PQ_cleanup_result (rs);
  }
}


/**
 * Return proposals whose timestamp are older than `date`.
 * Among those proposals, only those ones being between the
 * start-th and (start-nrows)-th record are returned.  The rows
 * are sorted having the youngest first.
 *
 * @param cls our plugin handle.
 * @param date only results older than this date are returned.
 * @param merchant_pub instance's public key; only rows related to this
 * instance are returned.
 * @param start only rows with serial id less than start are returned.
 * In other words, you lower `start` to get older records. The tipical
 * usage is to firstly call `find_contract_terms_by_date`, so that you get
 * the `nrows` youngest records. The oldest of those records will tell you
 * from which timestamp and `start` you can query the DB in order to get
 * furtherly older records, and so on. Alternatively, you can use always
 * the same timestamp and just go behind in history by tuning `start`.
 * @param nrows only nrows rows are returned.
 * @param future if set to GNUNET_YES, retrieves rows younger than `date`.
 * This is tipically used to show live updates on the merchant's backoffice
 * Web interface.
 * @param cb function to call with transaction data, can be NULL.
 * @param cb_cls closure for @a cb
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_find_contract_terms_by_date_and_range (void *cls,
						struct GNUNET_TIME_Absolute date,
						const struct TALER_MerchantPublicKeyP *merchant_pub,
						uint64_t start,
						uint64_t nrows,
						int future,
						TALER_MERCHANTDB_ProposalDataCallback cb,
						void *cb_cls)
{
  struct PostgresClosure *pg = cls;
  unsigned int yes = GNUNET_YES;

  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_absolute_time (&date),
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_uint64 (&start),
    GNUNET_PQ_query_param_uint64 (&nrows),
    GNUNET_PQ_query_param_auto_from_type (&yes),
    GNUNET_PQ_query_param_end
  };
  const char *stmt;
  enum GNUNET_DB_QueryStatus qs;
  struct FindContractsContext fcctx = {
    .cb = cb,
    .cb_cls = cb_cls
  };
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "DB serving /history with date %s\n",
              GNUNET_STRINGS_absolute_time_to_string (date));
  if (GNUNET_YES == future)
    stmt = "find_contract_terms_by_date_and_range_future";
  else
    stmt = "find_contract_terms_by_date_and_range";
  check_connection (pg);
  qs = GNUNET_PQ_eval_prepared_multi_select (pg->conn,
					     stmt,
					     params,
					     &find_contracts_cb,
					     &fcctx);
  if (0 >= qs)
    return qs;
  return fcctx.qs;
}


/**
 * Return proposals whose timestamp are older than `date`.
 * The rows are sorted having the youngest first.
 *
 * @param cls our plugin handle.
 * @param date only results older than this date are returned.
 * @param merchant_pub instance's public key; only rows related to this
 * instance are returned.
 * @param nrows at most nrows rows are returned.
 * @param cb function to call with transaction data, can be NULL.
 * @param cb_cls closure for @a cb
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_find_contract_terms_by_date (void *cls,
				      struct GNUNET_TIME_Absolute date,
				      const struct TALER_MerchantPublicKeyP *merchant_pub,
				      uint64_t nrows,
				      TALER_MERCHANTDB_ProposalDataCallback cb,
				      void *cb_cls)
{
  struct PostgresClosure *pg = cls;
  unsigned int yes = GNUNET_YES;

  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_absolute_time (&date),
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_uint64 (&nrows),
    GNUNET_PQ_query_param_auto_from_type (&yes),
    GNUNET_PQ_query_param_end
  };
  enum GNUNET_DB_QueryStatus qs;
  struct FindContractsContext fcctx = {
    .cb = cb,
    .cb_cls = cb_cls
  };

  check_connection (pg);
  qs = GNUNET_PQ_eval_prepared_multi_select (pg->conn,
					     "find_contract_terms_by_date",
					     params,
					     &find_contracts_cb,
					     &fcctx);
  if (0 >= qs)
    return qs;
  return fcctx.qs;
}


/**
 * Find information about a transaction.
 *
 * @param cls our plugin handle
 * @param h_contract_terms value used to perform the lookup
 * @param merchant_pub merchant's public key
 * @param cb function to call with transaction data
 * @param cb_cls closure for @a cb
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_find_transaction (void *cls,
                           const struct GNUNET_HashCode *h_contract_terms,
			   const struct TALER_MerchantPublicKeyP *merchant_pub,
                           TALER_MERCHANTDB_TransactionCallback cb,
                           void *cb_cls)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (h_contract_terms),
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_end
  };
  char *exchange_uri;
  struct GNUNET_HashCode h_wire;
  struct GNUNET_TIME_Absolute timestamp;
  struct GNUNET_TIME_Absolute refund_deadline;
  struct TALER_Amount total_amount;
  struct GNUNET_PQ_ResultSpec rs[] = {
    GNUNET_PQ_result_spec_string ("exchange_uri",
				  &exchange_uri),
    GNUNET_PQ_result_spec_auto_from_type ("h_wire",
					  &h_wire),
    GNUNET_PQ_result_spec_absolute_time ("timestamp",
					 &timestamp),
    GNUNET_PQ_result_spec_absolute_time ("refund_deadline",
					 &refund_deadline),
    TALER_PQ_result_spec_amount ("total_amount",
				 &total_amount),
    GNUNET_PQ_result_spec_end
  };
  enum GNUNET_DB_QueryStatus qs;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Finding transaction for h_contract_terms '%s', merchant_pub: '%s'.\n",
              GNUNET_h2s (h_contract_terms),
              TALER_B2S (merchant_pub));

  check_connection (pg);
  qs = GNUNET_PQ_eval_prepared_singleton_select (pg->conn,
						 "find_transaction",
						 params,
						 rs);
  if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
  {
    cb (cb_cls,
	merchant_pub,
        exchange_uri,
        h_contract_terms,
        &h_wire,
        timestamp,
        refund_deadline,
        &total_amount);
    GNUNET_PQ_cleanup_result (rs);
  }
  return qs;
}


/**
 * Closure for #find_payments_cb().
 */
struct FindPaymentsContext
{
  /**
   * Function to call with results.
   */
  TALER_MERCHANTDB_CoinDepositCallback cb;

  /**
   * Closure for @e cls.
   */
  void *cb_cls;

  /**
   * Contract term hash used for the search.
   */
  const struct GNUNET_HashCode *h_contract_terms;

  /**
   * Transaction status (set).
   */
  enum GNUNET_DB_QueryStatus qs;
};


/**
 * Function to be called with the results of a SELECT statement
 * that has returned @a num_results results.
 *
 * @param cls of type `struct FindPaymentsContext *`
 * @param result the postgres result
 * @param num_result the number of results in @a result
 */
static void
find_payments_cb (void *cls,
		  PGresult *result,
		  unsigned int num_results)
{
  struct FindPaymentsContext *fpc = cls;

  for (unsigned int i=0;i<num_results;i++)
  {
    struct TALER_CoinSpendPublicKeyP coin_pub;
    struct TALER_Amount amount_with_fee;
    struct TALER_Amount deposit_fee;
    struct TALER_Amount refund_fee;
    json_t *exchange_proof;
    struct GNUNET_PQ_ResultSpec rs[] = {
      GNUNET_PQ_result_spec_auto_from_type ("coin_pub",
                                            &coin_pub),
      TALER_PQ_result_spec_amount ("amount_with_fee",
                                   &amount_with_fee),
      TALER_PQ_result_spec_amount ("deposit_fee",
                                   &deposit_fee),
      TALER_PQ_result_spec_amount ("refund_fee",
                                   &refund_fee),
      TALER_PQ_result_spec_json ("exchange_proof",
                                 &exchange_proof),
      GNUNET_PQ_result_spec_end
    };

    if (GNUNET_OK !=
        GNUNET_PQ_extract_result (result,
                                  rs,
                                  i))
    {
      GNUNET_break (0);
      fpc->qs = GNUNET_DB_STATUS_HARD_ERROR;
      return;
    }
    fpc->qs = i + 1;
    fpc->cb (fpc->cb_cls,
	     fpc->h_contract_terms,
	     &coin_pub,
	     &amount_with_fee,
	     &deposit_fee,
	     &refund_fee,
	     exchange_proof);
    GNUNET_PQ_cleanup_result (rs);
  }
}


/**
 * Lookup information about coin payments by proposal data hash
 * (and @a merchant_pub)
 *
 * @param cls closure
 * @param h_contract_terms key for the search
 * @param merchant_pub merchant's public key
 * @param cb function to call with payment data
 * @param cb_cls closure for @a cb
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_find_payments (void *cls,
                        const struct GNUNET_HashCode *h_contract_terms,
		        const struct TALER_MerchantPublicKeyP *merchant_pub,
                        TALER_MERCHANTDB_CoinDepositCallback cb,
                        void *cb_cls)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (h_contract_terms),
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_end
  };
  struct FindPaymentsContext fpc = {
    .h_contract_terms = h_contract_terms,
    .cb = cb,
    .cb_cls = cb_cls
  };
  enum GNUNET_DB_QueryStatus qs;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Finding payment for h_contract_terms '%s'\n",
              GNUNET_h2s (h_contract_terms));
  check_connection (pg);
  qs = GNUNET_PQ_eval_prepared_multi_select (pg->conn,
					     "find_deposits",
					     params,
					     &find_payments_cb,
					     &fpc);
  if (qs <= 0)
    return qs;
  return fpc.qs;
}


/**
 * Closure for #find_payments_by_coin_cb().
 */
struct FindPaymentsByCoinContext
{
  /**
   * Function to call with results.
   */
  TALER_MERCHANTDB_CoinDepositCallback cb;

  /**
   * Closure for @e cls.
   */
  void *cb_cls;

  /**
   * Coin we are looking for.
   */
  const struct TALER_CoinSpendPublicKeyP *coin_pub;

  /**
   * Hash of the contract we are looking for.
   */
  const struct GNUNET_HashCode *h_contract_terms;

  /**
   * Transaction status (set).
   */
  enum GNUNET_DB_QueryStatus qs;
};


/**
 * Function to be called with the results of a SELECT statement
 * that has returned @a num_results results.
 *
 * @param cls of type `struct FindPaymentsByCoinContext *`
 * @param result the postgres result
 * @param num_result the number of results in @a result
 */
static void
find_payments_by_coin_cb (void *cls,
			  PGresult *result,
			  unsigned int num_results)
{
  struct FindPaymentsByCoinContext *fpc = cls;

  for (unsigned int i=0;i<num_results;i++)
  {
    struct TALER_Amount amount_with_fee;
    struct TALER_Amount deposit_fee;
    struct TALER_Amount refund_fee;
    json_t *exchange_proof;
    struct GNUNET_PQ_ResultSpec rs[] = {
      TALER_PQ_result_spec_amount ("amount_with_fee",
                                   &amount_with_fee),
      TALER_PQ_result_spec_amount ("deposit_fee",
                                   &deposit_fee),
      TALER_PQ_result_spec_amount ("refund_fee",
                                   &refund_fee),
      TALER_PQ_result_spec_json ("exchange_proof",
                                 &exchange_proof),
      GNUNET_PQ_result_spec_end
    };

    if (GNUNET_OK !=
        GNUNET_PQ_extract_result (result,
                                  rs,
                                  i))
    {
      GNUNET_break (0);
      fpc->qs = GNUNET_DB_STATUS_HARD_ERROR;
      return;
    }
    fpc->qs = i + 1;
    fpc->cb (fpc->cb_cls,
	     fpc->h_contract_terms,
	     fpc->coin_pub,
	     &amount_with_fee,
	     &deposit_fee,
	     &refund_fee,
	     exchange_proof);
    GNUNET_PQ_cleanup_result (rs);
  }
}


/**
 * Retrieve information about a deposited coin.
 *
 * @param cls closure
 * @param h_contract_terms hashcode of the proposal data paid by @a coin_pub
 * @param merchant_pub merchant's public key.
 * @param coin_pub coin's public key used for the search
 * @param cb function to call with payment data
 * @param cb_cls closure for @a cb
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_find_payments_by_hash_and_coin (void *cls,
                                         const struct GNUNET_HashCode *h_contract_terms,
                                         const struct TALER_MerchantPublicKeyP *merchant_pub,
                                         const struct TALER_CoinSpendPublicKeyP *coin_pub,
                                         TALER_MERCHANTDB_CoinDepositCallback cb,
                                         void *cb_cls)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (h_contract_terms),
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_auto_from_type (coin_pub),
    GNUNET_PQ_query_param_end
  };
  struct FindPaymentsByCoinContext fpc = {
    .cb = cb,
    .cb_cls = cb_cls,
    .h_contract_terms = h_contract_terms,
    .coin_pub = coin_pub
  };
  enum GNUNET_DB_QueryStatus qs;

  check_connection (pg);
  qs = GNUNET_PQ_eval_prepared_multi_select (pg->conn,
					     "find_deposits_by_hash_and_coin",
					     params,
					     &find_payments_by_coin_cb,
					     &fpc);
  if (0 >= qs)
    return qs;
  return fpc.qs;
}


/**
 * Closure for #find_transfers_cb().
 */
struct FindTransfersContext
{
  /**
   * Function to call on results.
   */
  TALER_MERCHANTDB_TransferCallback cb;

  /**
   * Closure for @e cb.
   */
  void *cb_cls;

  /**
   * Hash of the contract we are looking under.
   */
  const struct GNUNET_HashCode *h_contract_terms;

  /**
   * Transaction status (set).
   */
  enum GNUNET_DB_QueryStatus qs;
};


/**
 * Function to be called with the results of a SELECT statement
 * that has returned @a num_results results.
 *
 * @param cls of type `struct FindTransfersContext *`
 * @param result the postgres result
 * @param num_result the number of results in @a result
 */
static void
find_transfers_cb (void *cls,
		   PGresult *result,
		   unsigned int num_results)
{
  struct FindTransfersContext *ftc = cls;

  for (unsigned int i=0;i<PQntuples (result);i++)
  {
    struct TALER_CoinSpendPublicKeyP coin_pub;
    struct TALER_WireTransferIdentifierRawP wtid;
    struct GNUNET_TIME_Absolute execution_time;
    json_t *proof;

    struct GNUNET_PQ_ResultSpec rs[] = {
      GNUNET_PQ_result_spec_auto_from_type ("coin_pub",
                                            &coin_pub),
      GNUNET_PQ_result_spec_auto_from_type ("wtid",
                                            &wtid),
      GNUNET_PQ_result_spec_absolute_time ("execution_time",
                                           &execution_time),
      TALER_PQ_result_spec_json ("proof",
                                 &proof),
      GNUNET_PQ_result_spec_end
    };

    if (GNUNET_OK !=
        GNUNET_PQ_extract_result (result,
                                  rs,
                                  i))
    {
      GNUNET_break (0);
      ftc->qs = GNUNET_DB_STATUS_HARD_ERROR;
      return;
    }
    ftc->qs = i + 1;
    ftc->cb (ftc->cb_cls,
	     ftc->h_contract_terms,
	     &coin_pub,
	     &wtid,
	     execution_time,
	     proof);
    GNUNET_PQ_cleanup_result (rs);
  }
}


/**
 * Lookup information about a transfer by @a h_contract_terms.  Note
 * that in theory there could be multiple wire transfers for a
 * single @a h_contract_terms, as the transaction may have involved
 * multiple coins and the coins may be spread over different wire
 * transfers.
 *
 * @param cls closure
 * @param h_contract_terms key for the search
 * @param cb function to call with transfer data
 * @param cb_cls closure for @a cb
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_find_transfers_by_hash (void *cls,
                                 const struct GNUNET_HashCode *h_contract_terms,
                                 TALER_MERCHANTDB_TransferCallback cb,
                                 void *cb_cls)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (h_contract_terms),
    GNUNET_PQ_query_param_end
  };
  struct FindTransfersContext ftc = {
    .h_contract_terms = h_contract_terms,
    .cb = cb,
    .cb_cls = cb_cls
  };
  enum GNUNET_DB_QueryStatus qs;

  check_connection (pg);
  qs = GNUNET_PQ_eval_prepared_multi_select (pg->conn,
					     "find_transfers_by_hash",
					     params,
					     &find_transfers_cb,
					     &ftc);
  if (0 >= qs)
    return qs;
  return ftc.qs;
}


/**
 * Closure for #find_deposits_cb().
 */
struct FindDepositsContext
{

  /**
   * Function to call for each result.
   */
  TALER_MERCHANTDB_CoinDepositCallback cb;

  /**
   * Closure for @e cb.
   */
  void *cb_cls;

  /**
   * Transaction status (set).
   */
  enum GNUNET_DB_QueryStatus qs;
};


/**
 * Function to be called with the results of a SELECT statement
 * that has returned @a num_results results.
 *
 * @param cls of type `struct FindDepositsContext *`
 * @param result the postgres result
 * @param num_result the number of results in @a result
 */
static void
find_deposits_cb (void *cls,
		  PGresult *result,
		  unsigned int num_results)
{
  struct FindDepositsContext *fdc = cls;

  for (unsigned int i=0;i<PQntuples (result);i++)
  {
    struct GNUNET_HashCode h_contract_terms;
    struct TALER_CoinSpendPublicKeyP coin_pub;
    struct TALER_Amount amount_with_fee;
    struct TALER_Amount deposit_fee;
    struct TALER_Amount refund_fee;
    json_t *exchange_proof;
    struct GNUNET_PQ_ResultSpec rs[] = {
      GNUNET_PQ_result_spec_auto_from_type ("h_contract_terms",
                                            &h_contract_terms),
      GNUNET_PQ_result_spec_auto_from_type ("coin_pub",
                                            &coin_pub),
      TALER_PQ_result_spec_amount ("amount_with_fee",
                                   &amount_with_fee),
      TALER_PQ_result_spec_amount ("deposit_fee",
                                   &deposit_fee),
      TALER_PQ_result_spec_amount ("refund_fee",
                                   &refund_fee),
      TALER_PQ_result_spec_json ("exchange_proof",
                                 &exchange_proof),
      GNUNET_PQ_result_spec_end
    };

    if (GNUNET_OK !=
        GNUNET_PQ_extract_result (result,
                                  rs,
                                  i))
    {
      GNUNET_break (0);
      fdc->qs = GNUNET_DB_STATUS_HARD_ERROR;
      return;
    }
    fdc->qs = i + 1;
    fdc->cb (fdc->cb_cls,
	     &h_contract_terms,
	     &coin_pub,
	     &amount_with_fee,
	     &deposit_fee,
	     &refund_fee,
	     exchange_proof);
    GNUNET_PQ_cleanup_result (rs);
  }
}


/**
 * Lookup information about a coin deposits by @a wtid.
 *
 * @param cls closure
 * @param wtid wire transfer identifier to find matching transactions for
 * @param cb function to call with payment data
 * @param cb_cls closure for @a cb
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_find_deposits_by_wtid (void *cls,
                                const struct TALER_WireTransferIdentifierRawP *wtid,
                                TALER_MERCHANTDB_CoinDepositCallback cb,
                                void *cb_cls)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (wtid),
    GNUNET_PQ_query_param_end
  };
  struct FindDepositsContext fdc = {
    .cb = cb,
    .cb_cls = cb_cls
  };
  enum GNUNET_DB_QueryStatus qs;

  check_connection (pg);
  qs = GNUNET_PQ_eval_prepared_multi_select (pg->conn,
					     "find_deposits_by_wtid",
					     params,
					     &find_deposits_cb,
					     &fdc);
  if (0 >= qs)
    return qs;
  return fdc.qs;
}


/**
 * Closure for #get_refunds_cb().
 */
struct GetRefundsContext
{
  /**
   * Function to call for each refund.
   */
  TALER_MERCHANTDB_RefundCallback rc;

  /**
   * Closure for @e rc.
   */
  void *rc_cls;

  /**
   * Transaction result.
   */
  enum GNUNET_DB_QueryStatus qs;
};


/**
 * Function to be called with the results of a SELECT statement
 * that has returned @a num_results results.
 *
 * @param cls of type `struct GetRefundsContext *`
 * @param result the postgres result
 * @param num_result the number of results in @a result
 */
static void
get_refunds_cb (void *cls,
		PGresult *result,
		unsigned int num_results)
{
  struct GetRefundsContext *grc = cls;

  for (unsigned int i=0;i<num_results;i++)
  {
    struct TALER_CoinSpendPublicKeyP coin_pub;
    uint64_t rtransaction_id;
    struct TALER_Amount refund_amount;
    struct TALER_Amount refund_fee;
    char *reason;
    struct GNUNET_PQ_ResultSpec rs[] = {
      GNUNET_PQ_result_spec_auto_from_type ("coin_pub",
                                            &coin_pub),
      GNUNET_PQ_result_spec_uint64 ("rtransaction_id",
                                    &rtransaction_id),
      TALER_PQ_result_spec_amount ("refund_amount",
                                   &refund_amount),
      TALER_PQ_result_spec_amount ("refund_fee",
                                   &refund_fee),
      GNUNET_PQ_result_spec_string ("reason",
                                    &reason),
      GNUNET_PQ_result_spec_end
    };

    if (GNUNET_OK !=
        GNUNET_PQ_extract_result (result,
                                  rs,
                                  i))
    {
      GNUNET_break (0);
      grc->qs = GNUNET_DB_STATUS_HARD_ERROR;
      return;
    }
    grc->qs = i + 1;
    grc->rc (grc->rc_cls,
	     &coin_pub,
	     rtransaction_id,
	     reason,
	     &refund_amount,
	     &refund_fee);
    GNUNET_PQ_cleanup_result (rs);
  }
}


/**
 * Obtain refunds associated with a contract.
 *
 * @param cls closure, typically a connection to the db
 * @param merchant_pub public key of the merchant instance
 * @param h_contract_terms hash code of the contract
 * @param rc function to call for each coin on which there is a refund
 * @param rc_cls closure for @a rc
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_get_refunds_from_contract_terms_hash (void *cls,
                                               const struct TALER_MerchantPublicKeyP *merchant_pub,
                                               const struct GNUNET_HashCode *h_contract_terms,
                                               TALER_MERCHANTDB_RefundCallback rc,
                                               void *rc_cls)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_auto_from_type (h_contract_terms),
    GNUNET_PQ_query_param_end
  };
  struct GetRefundsContext grc = {
    .rc = rc,
    .rc_cls = rc_cls
  };
  enum GNUNET_DB_QueryStatus qs;

  TALER_LOG_DEBUG ("Looking for refund %s + %s\n",
                   GNUNET_h2s (h_contract_terms),
                   TALER_B2S (merchant_pub));

  check_connection (pg);
  qs = GNUNET_PQ_eval_prepared_multi_select (pg->conn,
					     "find_refunds_from_contract_terms_hash",
					     params,
					     &get_refunds_cb,
					     &grc);
  if (0 >= qs)
    return qs;
  return grc.qs;
}


/**
 * Insert a refund row into merchant_refunds.  Not meant to be exported
 * in the db API.
 *
 * @param cls closure, tipically a connection to the db
 * @param merchant_pub merchant instance public key
 * @param h_contract_terms hashcode of the contract related to this refund
 * @param coin_pub public key of the coin giving the (part of) refund
 * @param reason human readable explaination behind the refund
 * @param refund how much this coin is refunding
 * @param refund_fee refund fee for this coin
 */
enum GNUNET_DB_QueryStatus
insert_refund (void *cls,
               const struct TALER_MerchantPublicKeyP *merchant_pub,
               const struct GNUNET_HashCode *h_contract_terms,
               const struct TALER_CoinSpendPublicKeyP *coin_pub,
               const char *reason,
               const struct TALER_Amount *refund,
               const struct TALER_Amount *refund_fee)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_auto_from_type (h_contract_terms),
    GNUNET_PQ_query_param_auto_from_type (coin_pub),
    GNUNET_PQ_query_param_string (reason),
    TALER_PQ_query_param_amount (refund),
    TALER_PQ_query_param_amount (refund_fee),
    GNUNET_PQ_query_param_end
  };

  TALER_LOG_DEBUG ("Inserting refund %s + %s\n",
                   GNUNET_h2s (h_contract_terms),
                   TALER_B2S (merchant_pub));

  check_connection (pg);
  return GNUNET_PQ_eval_prepared_non_select (pg->conn,
                                             "insert_refund",
                                             params);
}


/**
 * Store information about wire fees charged by an exchange,
 * including signature (so we have proof).
 *
 * @param cls closure
 * @paramm exchange_pub public key of the exchange
 * @param h_wire_method hash of wire method
 * @param wire_fee wire fee charged
 * @param closing_fee closing fee charged (irrelevant for us,
 *              but needed to check signature)
 * @param start_date start of fee being used
 * @param end_date end of fee being used
 * @param exchange_sig signature of exchange over fee structure
 * @return transaction status code
 */
static enum GNUNET_DB_QueryStatus
postgres_store_wire_fee_by_exchange (void *cls,
				     const struct TALER_MasterPublicKeyP *exchange_pub,
				     const struct GNUNET_HashCode *h_wire_method,
				     const struct TALER_Amount *wire_fee,
				     const struct TALER_Amount *closing_fee,
				     struct GNUNET_TIME_Absolute start_date,
				     struct GNUNET_TIME_Absolute end_date,
				     const struct TALER_MasterSignatureP *exchange_sig)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (exchange_pub),
    GNUNET_PQ_query_param_auto_from_type (h_wire_method),
    TALER_PQ_query_param_amount (wire_fee),
    TALER_PQ_query_param_amount (closing_fee),
    GNUNET_PQ_query_param_absolute_time (&start_date),
    GNUNET_PQ_query_param_absolute_time (&end_date),
    GNUNET_PQ_query_param_auto_from_type (exchange_sig),
    GNUNET_PQ_query_param_end
  };

  check_connection (pg);
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
	      "Storing wire fee for %s starting at %s of %s\n",
	      TALER_B2S (exchange_pub),
	      GNUNET_STRINGS_absolute_time_to_string (start_date),
	      TALER_amount2s (wire_fee));
  return GNUNET_PQ_eval_prepared_non_select (pg->conn,
                                             "insert_wire_fee",
                                             params);
}


/**
 * Obtain information about wire fees charged by an exchange,
 * including signature (so we have proof).
 *
 * @param cls closure
 * @param exchange_pub public key of the exchange
 * @param h_wire_method hash of wire method
 * @param contract_date date of the contract to use for the lookup
 * @param[out] wire_fee wire fee charged
 * @param[out] closing_fee closing fee charged (irrelevant for us,
 *              but needed to check signature)
 * @param[out] start_date start of fee being used
 * @param[out] end_date end of fee being used
 * @param[out] exchange_sig signature of exchange over fee structure
 * @return transaction status code
 */
static enum GNUNET_DB_QueryStatus
postgres_lookup_wire_fee (void *cls,
			  const struct TALER_MasterPublicKeyP *exchange_pub,
			  const struct GNUNET_HashCode *h_wire_method,
			  struct GNUNET_TIME_Absolute contract_date,
			  struct TALER_Amount *wire_fee,
			  struct TALER_Amount *closing_fee,
			  struct GNUNET_TIME_Absolute *start_date,
			  struct GNUNET_TIME_Absolute *end_date,
			  struct TALER_MasterSignatureP *exchange_sig)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (exchange_pub),
    GNUNET_PQ_query_param_auto_from_type (h_wire_method),
    GNUNET_PQ_query_param_absolute_time (&contract_date),
    GNUNET_PQ_query_param_end
  };
  struct GNUNET_PQ_ResultSpec rs[] = {
    TALER_PQ_result_spec_amount ("wire_fee",
				 wire_fee),
    TALER_PQ_result_spec_amount ("closing_fee",
				 closing_fee),
    GNUNET_PQ_result_spec_absolute_time ("start_date",
					 start_date),
    GNUNET_PQ_result_spec_absolute_time ("end_date",
					 end_date),
    GNUNET_PQ_result_spec_auto_from_type ("exchange_sig",
					  exchange_sig),
    GNUNET_PQ_result_spec_end
  };

  check_connection (pg);
  return GNUNET_PQ_eval_prepared_singleton_select (pg->conn,
						   "lookup_wire_fee",
						   params,
						   rs);
}


/**
 * Closure for #process_refund_cb.
 */
struct FindRefundContext
{
  /**
   * Updated to reflect total amount refunded so far.
   */
  struct TALER_Amount refunded_amount;

  /**
   * Set to #GNUNET_SYSERR on hard errors.
   */
  int err;
};


/**
 * Function to be called with the results of a SELECT statement
 * that has returned @a num_results results.
 *
 * @param cls closure, our `struct FindRefundContext`
 * @param result the postgres result
 * @param num_result the number of results in @a result
 */
static void
process_refund_cb (void *cls,
                   PGresult *result,
                   unsigned int num_results)
{
  struct FindRefundContext *ictx = cls;

  for (unsigned int i=0; i<num_results; i++)
  {
    /* Sum up existing refunds */
    struct TALER_Amount acc;
    struct GNUNET_PQ_ResultSpec rs[] = {
      TALER_PQ_result_spec_amount ("refund_amount",
                                   &acc),
      GNUNET_PQ_result_spec_end
    };

    if (GNUNET_OK !=
        GNUNET_PQ_extract_result (result,
                                  rs,
                                  i))
    {
      GNUNET_break (0);
      ictx->err = GNUNET_SYSERR;
      return;
    }
    if (GNUNET_SYSERR ==
        TALER_amount_add (&ictx->refunded_amount,
                          &ictx->refunded_amount,
                          &acc))
    {
      GNUNET_break (0);
      ictx->err = GNUNET_SYSERR;
      return;
    }
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Found refund of %s\n",
                TALER_amount2s (&acc));
  }
}


/**
 * Closure for #process_deposits_cb.
 */
struct InsertRefundContext
{
  /**
   * Used to provide a connection to the db
   */
  struct PostgresClosure *pg;

  /**
   * Amount to which increase the refund for this contract
   */
  const struct TALER_Amount *refund;

  /**
   * Merchant instance public key
   */
  const struct TALER_MerchantPublicKeyP *merchant_pub;

  /**
   * Hash code representing the contract
   */
  const struct GNUNET_HashCode *h_contract_terms;

  /**
   * Human-readable reason behind this refund
   */
  const char *reason;

  /**
   * Transaction status code.
   */
  enum GNUNET_DB_QueryStatus qs;
};


/**
 * Function to be called with the results of a SELECT statement
 * that has returned @a num_results results.
 *
 * @param cls closure, our `struct InsertRefundContext`
 * @param result the postgres result
 * @param num_result the number of results in @a result
 */
static void
process_deposits_for_refund_cb (void *cls,
				PGresult *result,
				unsigned int num_results)
{
  struct InsertRefundContext *ctx = cls;
  struct TALER_Amount current_refund;
  struct TALER_Amount deposit_refund[num_results];
  struct TALER_CoinSpendPublicKeyP deposit_coin_pubs[num_results];
  struct TALER_Amount deposit_amount_with_fee[num_results];
  struct TALER_Amount deposit_refund_fee[num_results];

  TALER_amount_get_zero (ctx->refund->currency,
                         &current_refund);

  /* Pass 1:  Collect amount of existing refunds into current_refund.
   * Also store existing refunded amount for each deposit in deposit_refund. */

  for (unsigned int i=0; i<num_results; i++)
  {
    struct TALER_CoinSpendPublicKeyP coin_pub;
    struct TALER_Amount amount_with_fee;
    struct TALER_Amount refund_fee;
    struct GNUNET_PQ_ResultSpec rs[] = {
      GNUNET_PQ_result_spec_auto_from_type ("coin_pub",
                                            &coin_pub),
      TALER_PQ_result_spec_amount ("amount_with_fee",
                                   &amount_with_fee),
      TALER_PQ_result_spec_amount ("refund_fee",
                                   &refund_fee),
      GNUNET_PQ_result_spec_end
    };

    if (GNUNET_OK !=
        GNUNET_PQ_extract_result (result,
                                  rs,
                                  i))
    {
      GNUNET_break (0);
      ctx->qs = GNUNET_DB_STATUS_HARD_ERROR;
      return;
    }

    struct FindRefundContext ictx;
    enum GNUNET_DB_QueryStatus ires;
    struct GNUNET_PQ_QueryParam params[] = {
      GNUNET_PQ_query_param_auto_from_type (&coin_pub),
      GNUNET_PQ_query_param_end
    };

    TALER_amount_get_zero (ctx->refund->currency,
                           &ictx.refunded_amount);
    ictx.err = GNUNET_OK; /* no error so far */
    ires = GNUNET_PQ_eval_prepared_multi_select (ctx->pg->conn,
                                                 "find_refunds",
                                                 params,
                                                 &process_refund_cb,
                                                 &ictx);
    if ( (GNUNET_OK != ictx.err) ||
         (GNUNET_DB_STATUS_HARD_ERROR == ires) )
    {
      GNUNET_break (0);
      ctx->qs = GNUNET_DB_STATUS_HARD_ERROR;
      return;
    }
    if (GNUNET_DB_STATUS_SOFT_ERROR == ires)
    {
      ctx->qs = GNUNET_DB_STATUS_SOFT_ERROR;
      return;
    }
    deposit_refund[i] = ictx.refunded_amount;
    deposit_amount_with_fee[i] = amount_with_fee;
    deposit_coin_pubs[i] = coin_pub;
    deposit_refund_fee[i] = refund_fee;
    if (GNUNET_SYSERR ==
	TALER_amount_add (&current_refund,
			  &current_refund,
			  &ictx.refunded_amount))
    {
      GNUNET_break (0);
      ctx->qs = GNUNET_DB_STATUS_HARD_ERROR;
      return;
    }
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Existing refund for coin %s is %s\n",
                TALER_B2S (&coin_pub),
                TALER_amount2s (&ictx.refunded_amount));
  }

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Total existing refund is %s\n",
              TALER_amount2s (&current_refund));

  /* stop immediately if we are done */
  if (0 == TALER_amount_cmp (ctx->refund,
                             &current_refund))
    return;


  /* Phase 2:  Try to increase current refund until it matches desired refund */

  for (unsigned int i=0; i<num_results; i++)
  {
    const struct TALER_Amount *increment;
    struct TALER_Amount left;

    /* How much of the coin is left after the existing refunds? */
    if (GNUNET_SYSERR ==
	TALER_amount_subtract (&left,
			       &deposit_amount_with_fee[i],
			       &deposit_refund[i]))
    {
      GNUNET_break (0);
      ctx->qs = GNUNET_DB_STATUS_HARD_ERROR;
      return;
    }

    if ( (0 == left.value) &&
	 (0 == left.fraction) )
    {
      /* coin was fully refunded, move to next coin */
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
		  "Coin %s fully refunded, moving to next coin\n",
		  TALER_B2S (&deposit_coin_pubs[i]));
      continue;
    }

    struct TALER_Amount remaining_refund;

    /* How much of the refund is left? */
    if (GNUNET_SYSERR ==
	TALER_amount_subtract (&remaining_refund,
			       ctx->refund,
			       &current_refund))
    {
      GNUNET_break (0);
      ctx->qs = GNUNET_DB_STATUS_HARD_ERROR;
      return;
    }

    /* By how much will we increase the refund for this coin? */
    if (0 >= TALER_amount_cmp (&remaining_refund,
			       &left))
    {
      /* remaining_refund <= left */
      increment = &remaining_refund;
    }
    else
    {
      increment = &left;
    }

    if (GNUNET_SYSERR ==
	TALER_amount_add (&current_refund,
			  &current_refund,
			  increment))
    {
      GNUNET_break (0);
      ctx->qs = GNUNET_DB_STATUS_HARD_ERROR;
      return;
    }

    /* actually run the refund */
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
		"Coin %s deposit amount is %s\n",
		TALER_B2S (&deposit_coin_pubs[i]),
		TALER_amount2s (&deposit_amount_with_fee[i]));
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
		"Coin %s refund will be incremented by %s\n",
		TALER_B2S (&deposit_coin_pubs[i]),
		TALER_amount2s (increment));
    {
      enum GNUNET_DB_QueryStatus qs;

      if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT !=
	  (qs = insert_refund (ctx->pg,
			       ctx->merchant_pub,
			       ctx->h_contract_terms,
			       &deposit_coin_pubs[i],
			       ctx->reason,
			       increment,
			       &deposit_refund_fee[i])))
      {
	GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR == qs);
	ctx->qs = qs;
	return;
      }
    }
    /* stop immediately if we are done */
    if (0 == TALER_amount_cmp (ctx->refund,
                               &current_refund))
      return;
  }

  /**
   * We end up here if nto all of the refund has been covered.
   * Although this should be checked as the business should never
   * issue a refund bigger than the contract's actual price, we cannot
   * rely upon the frontend being correct.
   */
  GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
	      "The refund of %s is bigger than the order's value\n",
	      TALER_amount2s (ctx->refund));
  ctx->qs = GNUNET_DB_STATUS_HARD_ERROR;
}


/**
 * Function called when some backoffice staff decides to award or
 * increase the refund on an existing contract.
 *
 * @param cls closure
 * @param h_contract_terms
 * @param merchant_pub merchant's instance public key
 * @param refund maximum refund to return to the customer for this contract
 * @param reason 0-terminated UTF-8 string giving the reason why the customer
 *               got a refund (free form, business-specific)
 * @return transaction status
 *         #GNUNET_DB_STATUS_SUCCESS_ONE_RESULT if the refund is accepted
 *         #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if the refund cannot be issued: this can happen for two
 *               reasons: the issued refund is not greater of the previous refund,
 *               or the coins don't have enough amount left to pay for this refund.
 */
static enum GNUNET_DB_QueryStatus
postgres_increase_refund_for_contract (void *cls,
                                       const struct GNUNET_HashCode *h_contract_terms,
                                       const struct TALER_MerchantPublicKeyP *merchant_pub,
                                       const struct TALER_Amount *refund,
                                       const char *reason)
{
  struct PostgresClosure *pg = cls;
  struct InsertRefundContext ctx;
  enum GNUNET_DB_QueryStatus qs;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (h_contract_terms),
    GNUNET_PQ_query_param_auto_from_type (merchant_pub),
    GNUNET_PQ_query_param_end
  };

  if (GNUNET_OK !=
      postgres_start (cls))
  {
    GNUNET_break (0);
    return GNUNET_DB_STATUS_HARD_ERROR;
  }
  ctx.pg = pg;
  ctx.qs = GNUNET_DB_STATUS_SUCCESS_ONE_RESULT;
  ctx.refund = refund;
  ctx.reason = reason;
  ctx.h_contract_terms = h_contract_terms;
  ctx.merchant_pub = merchant_pub;
  qs = GNUNET_PQ_eval_prepared_multi_select (pg->conn,
					     "find_deposits",
					     params,
					     &process_deposits_for_refund_cb,
					     &ctx);
  switch (qs)
  {
  case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Unknown contract: %s (merchant_pub: %s), no refund possible\n",
                GNUNET_h2s (h_contract_terms),
                TALER_B2S (merchant_pub));
    postgres_rollback (cls);
    return qs;
  case GNUNET_DB_STATUS_SOFT_ERROR:
  case GNUNET_DB_STATUS_HARD_ERROR:
    postgres_rollback (cls);
    return qs;
  default:
    /* Got one or more deposits */
    if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != ctx.qs)
    {
      postgres_rollback (cls);
      return ctx.qs;
    }
    qs = postgres_commit (cls);
    if (0 > qs)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                  "Failed to commit transaction increasing refund\n");
      return qs;
    }
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
		"Committed refund transaction\n");
    return ctx.qs;
  }
}


/**
 * Lookup proof information about a wire transfer.
 *
 * @param cls closure
 * @param exchange_uri from which exchange are we looking for proof
 * @param wtid wire transfer identifier for the search
 * @param cb function to call with proof data
 * @param cb_cls closure for @a cb
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
postgres_find_proof_by_wtid (void *cls,
                             const char *exchange_uri,
                             const struct TALER_WireTransferIdentifierRawP *wtid,
                             TALER_MERCHANTDB_ProofCallback cb,
                             void *cb_cls)
{
  struct PostgresClosure *pg = cls;
  struct GNUNET_PQ_QueryParam params[] = {
    GNUNET_PQ_query_param_auto_from_type (wtid),
    GNUNET_PQ_query_param_string (exchange_uri),
    GNUNET_PQ_query_param_end
  };
  json_t *proof;
  struct GNUNET_PQ_ResultSpec rs[] = {
    TALER_PQ_result_spec_json ("proof",
			       &proof),
    GNUNET_PQ_result_spec_end
  };
  enum GNUNET_DB_QueryStatus qs;

  check_connection (pg);
  qs = GNUNET_PQ_eval_prepared_singleton_select (pg->conn,
						 "find_proof_by_wtid",
						 params,
						 rs);
  if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
  {
    cb (cb_cls,
        proof);
    GNUNET_PQ_cleanup_result (rs);
  }
  return qs;
}


/**
 * Initialize Postgres database subsystem.
 *
 * @param cls a configuration instance
 * @return NULL on error, otherwise a `struct TALER_MERCHANTDB_Plugin`
 */
void *
libtaler_plugin_merchantdb_postgres_init (void *cls)
{
  struct GNUNET_CONFIGURATION_Handle *cfg = cls;
  struct PostgresClosure *pg;
  struct TALER_MERCHANTDB_Plugin *plugin;
  const char *ec;

  pg = GNUNET_new (struct PostgresClosure);
  ec = getenv ("TALER_MERCHANTDB_POSTGRES_CONFIG");
  if (NULL != ec)
  {
    GNUNET_CONFIGURATION_set_value_string (cfg,
                                           "merchantdb-postgres",
                                           "CONFIG",
                                           ec);
  }
  else
  {
    if (GNUNET_OK !=
        GNUNET_CONFIGURATION_have_value (cfg,
                                         "merchantdb-postgres",
                                         "CONFIG"))
    {
      GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
                                 "merchantdb-postgres",
                                 "CONFIG");
      return NULL;
    }
  }
  pg->cfg = cfg;
  pg->conn = GNUNET_PQ_connect_with_cfg (cfg,
                                         "merchantdb-postgres");
  if (NULL == pg->conn)
  {
    GNUNET_free (pg);
    return NULL;
  }
  plugin = GNUNET_new (struct TALER_MERCHANTDB_Plugin);
  plugin->cls = pg;
  plugin->drop_tables = &postgres_drop_tables;
  plugin->initialize = &postgres_initialize;
  plugin->store_transaction = &postgres_store_transaction;
  plugin->store_deposit = &postgres_store_deposit;
  plugin->store_coin_to_transfer = &postgres_store_coin_to_transfer;
  plugin->store_transfer_to_proof = &postgres_store_transfer_to_proof;
  plugin->store_wire_fee_by_exchange = &postgres_store_wire_fee_by_exchange;
  plugin->find_transaction = &postgres_find_transaction;
  plugin->find_payments_by_hash_and_coin = &postgres_find_payments_by_hash_and_coin;
  plugin->find_payments = &postgres_find_payments;
  plugin->find_transfers_by_hash = &postgres_find_transfers_by_hash;
  plugin->find_deposits_by_wtid = &postgres_find_deposits_by_wtid;
  plugin->find_proof_by_wtid = &postgres_find_proof_by_wtid;
  plugin->insert_contract_terms = &postgres_insert_contract_terms;
  plugin->find_contract_terms = &postgres_find_contract_terms;
  plugin->find_contract_terms_history = &postgres_find_contract_terms_history;
  plugin->find_contract_terms_by_date = &postgres_find_contract_terms_by_date;
  plugin->find_contract_terms_by_date_and_range = &postgres_find_contract_terms_by_date_and_range;
  plugin->find_contract_terms_from_hash = &postgres_find_contract_terms_from_hash;
  plugin->get_refunds_from_contract_terms_hash = &postgres_get_refunds_from_contract_terms_hash;
  plugin->lookup_wire_fee = &postgres_lookup_wire_fee;
  plugin->increase_refund_for_contract = postgres_increase_refund_for_contract;
  plugin->mark_proposal_paid = postgres_mark_proposal_paid;
  plugin->start = postgres_start;
  plugin->commit = postgres_commit;
  plugin->rollback = postgres_rollback;

  return plugin;
}


/**
 * Shutdown Postgres database subsystem.
 *
 * @param cls a `struct TALER_MERCHANTDB_Plugin`
 * @return NULL (always)
 */
void *
libtaler_plugin_merchantdb_postgres_done (void *cls)
{
  struct TALER_MERCHANTDB_Plugin *plugin = cls;
  struct PostgresClosure *pg = plugin->cls;

  PQfinish (pg->conn);
  GNUNET_free (pg);
  GNUNET_free (plugin);
  return NULL;
}

/* end of plugin_merchantdb_postgres.c */